Highly Reproducible Synthesis of PbS Quantum Dots With In Situ Halide Passivation for Short-Wave Infrared Imaging Chips.

PbS colloidal quantum dots (QDs) have become promising materials for short-wave infrared (SWIR) detection and imaging due to their solution processability and monolithic integration with readout circuits. As the light-absorbing materials, PbS QDs serve as the core components for imaging chips, thus synthesis of high-quality PbS QDs is crucial for the development of QD imaging technology. Current synthetic methods of PbS QDs cannot achieve efficient surface passivation, high monodispersity, accurate size control, and high reproducibility, simultaneously. In the present work, a highly reproducible synthesis of high-quality PbS QDs is developed, by applying ethyl ziram (EZ) as the sulfur source. The most striking feature of this synthesis is the self-terminated growth, rendering it with high reproducibility. The self-terminated growth arises from a stable surface configuration, including surface atom arrangement and ligand-surface atom interaction. The as-synthesized PbS QDs show higher photoluminescence quantum yields than those synthesized by the cation exchange method, confirming the stable surface configuration. Due to the excellent surface passivation, these PbS QDs also exhibit better photodetector performance, demonstrated by lower dark currents and higher external quantum efficiencies. Finally, monolithically integrated SWIR imaging chips are fabricated using the PbS QDs synthesized from EZ, demonstrating excellent imaging performance.